Vessels or drums of various sizes and shapes are used commercially to store, ship and dispense various substances. An opening is provided in the vessel or its lid to allow the vessel to be filled and to allow the contents of the vessel to be dispensed. The vessel opening is typically sealed with a removable bung or cap. The bung is typically threaded into the opening and forms a seal to prevent the contents from escaping from the vessel.
In order to provide an indication of prior access to the contents of the vessel, a tamper evident cover may be placed over the bung. Certain existing covers or other closures for this purpose use a tear strip along the skirt of the cover that must be removed to remove the cover. A pull-tab or ring is attached to the tear strip, and when the tab or ring is pulled, the tear strip is torn, and the cover may be removed from the vessel. A torn or missing tear strip evidences prior removal of the cover and possible tampering with the contents of the vessel.
An example of such a tamper evident cap is shown in U.S. Pat. No. 5,875,908 to Witt, et al. which shows a reusable bottle cap with a removable tamper evident tear strip or ring. In the Witt device, a plurality of teeth on the tear strip snap under a shoulder on the neck of a milk bottle so that the cap cannot be removed without first removing the tear strip. The tear strip is separable from the cap by a series of frangible tabs, and the tear strip includes a pull ring. When the pull ring is pulled to remove the tear strip, the tabs are broken in series, and the tear strip is separated from the cap. The tear strip is an open annulus so when it is separated from the cap, it can be removed from the bottleneck.
While this may have represented an improvement over former milk bottle closures such as friction fitted cardboard disks, crimped on aluminum foil caps, or crimped on paper caps, it does not provide a sufficient level of tamper evident security to meet current demands. Although the plurality of teeth of Witt will retain the cap and tear strip to the bottle, it is still possible to bend the individual teeth of the Witt device one at a time and effect removal of the cap without destroying the cap, thereby permitting removal and replacement of the cap without detection.
While this may not present a significant risk for a bottle of milk, it could be a concern for a larger container such as a drum that might contain a food product, perhaps in concentrated form that will be distributed to a large number of consumers, or it might contain a precious material, such as an expensive fragrance. In addition, with today's increased focus on security, even a humble milk bottle would benefit in the eyes of the consuming public from a higher level of security.
U.S. Pat. No. 5,944,229 to Rokkjaer discloses a tamper evident cap for a drum in which the cap has a ledge that snaps under a capturing surface on the drum. When a frangible strip is pulled, the cap is partially torn, and evidence of removal or possible tampering is provided. However, when the strip is removed, it is still necessary to compress the two severed halves of the cap together to effect release of the ledge from the capturing surface on the drum. With this arrangement, while a secure tamper evident cap is provided, the cap is difficult to install, and even more difficult to remove, requiring specific training of personnel at both the filling and dispensing ends of the shipping or storage cycle of the drum.
Another tamper evident cap for use with a drum is shown in U.S. Pat. No. 5,996,833 to Lencioni, et al. In that reference, a locking annular ring snaps under a lip formed on a neck of the drum, but must forced onto the neck with great effort with only two major and two minor slots to allow deformation of the ring to pass over the lip and into locked position.